Stud-driving apparatus



Oct. 1, 1963 M, HlL-Tl STUD-DRIVING APPARATUS 5 Sheets-Sheet l Filed Feb. 13, 1961 INVENTOR Martin Hlltl ATTORNEYS Oct. 1, 1963 M. HxLTl STUD-DRIVING APPARATUS 5 sheets-sheet 2v Filed Feb. 13. 1961 Oct. 1, 1963 M. HlLTl 3,105,238

' STUD-DRIVING APPARATUS v Filed Feb. 13, 1961 5 sheets-sheet s lNVEN-TOR. Martin Hilti BY @afd/.i3 //f/lsywd ATTORNEYS Oct. 1, 1963 M. HILTI v STUD-DRIVING APPARATUS 5 Sheets-,Sheet 4 Filed Feb. 13, 1961 ATTORNEYS oct. 1, 1963 l M, Hlm 3,105,238

STUD-DRIVING APPARATUS Filed Feb. 15. 1961 5 Sheets-Sheet 5 NVENTOR Martin Hilii BY @aft/5i] /fr/'gfayf/am ATTORNEYS Uted States Patent O 3,105,238 SIUE-DRIVING APIARA'IUS Martin Hilti, Vadus, `Liechtenstein, assigner to Anstalt fr Montagefeclmilr, Vedas, Liechtenstein Filed Feb. I3, i951, Ser. No. 8%,943 Claims priority, application Germany Dee. 5, 1969 I8 llaims. (Cl. llt-44.5)

This invention relates to stud-driving apparatus for the insertion of anchoring studs into hard materials such as concrete or iron, and wherein the stud is driven by a piston impelled `by the combustion gases of a cartridge. One such apparatus comprises a cylindrical shell adapted to be held in the hand and having at one end a shield aifording protection against flying splinters resulting from the studdriving operation. Slidably mounted in this shell is a guide tube within which the piston and a cartridge holder are independently axially movable. The cartridge holder is formed in its fonward end with a cavity arranged to support the cartridge with its ibase facing the piston. The apparatus is so constructed that the cartridge cannot be ignited until :the splinter shield has been properly positioned, i.e. until the mouth of the guide tube has been aligned with the forward plane of the splinter shield, as a result of pressing the tool against the work surface into which the stud is to be driven.

In tools of the type wherein the cartridge holder is moved by spring tension against the piston, this safety feature is achieved by arranging the axially movable guide tube in such a manner that it blocks the trigger mechanism except when the forward surface of its mouth lies in the forward plane of the splinter shield. In tools of the type wherein the cartridge holder is driven forward by a blow to bring the cartridge base into contact with an ignition pin on the piston, protection against undesired ignitions is accomplished by providing the adjacent ends of the piston and the cartridge holder with projections which will only permit such contact when the piston and cartridge holder have a certain rotary position relative to one another, this rotary position being achieved by pushing the guide tube into the tool by pressing it against the work surface.

In the latter case, the cartridge carrier is non-rotatably mounted with respect to the outer shell carrying the movable guide tube, and is provided on its rearward end with a hammering surface which serves as a recoil damping mass. On the other hand, the piston is non-rotatably movable in the guide tube and is rotatable with .this tube, in a limited fashion, through the action of a cam mounted on the tube, which cam permits limited rotation in a guide cut into the gripping shell. This limited movement is such that the relative rotary positioning required for ignition is reached only after the piston and the guide tube, under the inuence of the guide cut into the gripping shell, have carried out a partial rotation due to an inward shifting of the guide tube `by pressing the tool against the work surface.

Further details of the invention can be found in the following description considered together with the accompanying drawings, in which:

FIGURES la and 1b show two cooperating units of a tool in axial longitudinal section, the first unit comprising the gripping shell with the splinter shield and guide tube and the second -unit comprising the cartridge carrier;

FIGURE 2 shows the tool of FIGURE 1 after the cartridge carrier is placed in the guide tube, but before the tool has been placed against ythe work surface;

FIGURE 3 shows the tool of FIGURE l after placing it against the work surface and directly before firing.

FIGURE 4 is a cross section through the guide tube along lines IV-IV of FIGURE l;

lCe

FIGURES 5a and 5b show on a larger scale, in front view and in side view, a plastic washer which is placed on the point of the anchoring stud;

FIGURE 6 is a sectional View through another embodiment of a plastic washer;

FIGURE 7 shows in vertical axial cross-section another embodiment of the invention, Without the guide tube and the piston;

FIGURE 8 shows the gui-de tube and piston for the tool of FIGURE 7;

FIGURE 9 shows the assembled tool of FIGURES 7 and 8 with the `guide tube moved forward into the safe position;

FIGURE l0 shows the tool of FIGURE 9 in ready position for firing;

FIGURE ll is a cross-section along the line XI-XI of FIGURE 7;

FIGURE l2 is a cross-Section along the line XII-XII of FIGURE 8;

FIGURES 13 and 14 schematically show the two sets of engageable teeth together with the cam elements employed to produce relative motion between the teeth, these teeth being shown in the two gures in different opposing positions of the circle of .teeth in conjunction with the corresponding position of the cam in the slotted guides; and

FIGURE 15 is ya perspective view of the piston of the apparatus shown in FIGURES 7 to 10.

The stud-driving ytool shown in FIGURES l to 4 comprises a housing 1, surrounded by a gripping shell 10, and having at its forward end a splinter shield 3. Slidably mounted within this housing is a guide tube 2 carrying a piston 4. Shiftable into the guide tube is a cartridge carrier 5 having an interchangeable cartridge holder 6, tensioning spring 7, and the tubularly formed head piece S with gripping knob 9.

The rearward end 1I of piston 4 has a cavity shaped to receive the cartridge holder 6, and is provided with a tiring pin 12 arranged to contact the base of cartridge 13 when the cartridge holder has been driven forward by spring 7.

In the inner wall of the guide tube 2 are eight axial grooves I4. These begin near the place in which the cartridge holder 6 is located when in tiring position as shown in FIGURE 3. At their other end, the grooves I4 communicate, when in firing position (FIGURE 3), with the interior of the splinter shield 3, and through it to Vthe outside.

The cartridge holder 6 is interchangeably mounted in a corresponding cavity on the forward end of the cartridge carrier 5 by means of a pin 16 extending through a hole 17 diametrically located in cartridge carrier 5. Dead-end cavity 52, which terminates in a pointed end, communicates with the cavity which holds cartridge I3. The cartridge carrier 5 has a central cavity 18 which holds spring 7 in an expanded condition. The rearward end of the cartridge carrier 5 leads into head piece 8 which is tubularly shaped and adapted to t into housing l, and which is closed on that end not receiving cartridge carrier 5. Head piece 8 can be locked in position by a bayonet closure in which cams 19 lock into the cavity Zit of the housing 1.

That portion of the spring 7 which lies in head piece 8 is guided therein on a central pin 48. For absorption of the recoil of the cartridge carrier 5, plate springs ZI are arranged at the end of tubular head piece 8 which extends into axial cavity 3-7, of corresponding diameter, and a helical spring 22 is positioned between knob and rim 36 of head piece 8.

The rearward end of guide tube 2 is slightly tapered to accommodate insertion of the cartridge carrier 5 during struction.

assembly of the apparatus after loading. The length of guide turbe Z is so chosen that, when in tiring position (FIGURE 3), a space remains between .the iring pin 12 and the base of cartridge 13.

At its mouth end 24, guide tube 2 is provided with a cylindrical extension 25 having stepped inner walls. This extension -25 is retained on guide tube 2i by element 25. The narrower portion 28', which serves to accept a positioning washer 2:7 for anchoring stud 23, is so arranged that the lower end of the piston 4 can protrude therethrough. Piston 4 is provided with a circular shoulder 35 so located that it contacts the cylindrical casing 25 when the forward end 29 of the piston protrudes a small amount from narrower portion 28.

The positioning washer 27 which holds the anchoring stud in opening Z8 serves in a known fashion for the centering and positioning of the anchoring stud 23. It can, for example, be made of metal or plastic. If it is desired that the positioning washer be destroyed after the `driving in of the anchoring stud, it is suitably made of a brittle material such as :a hardened resin or plastic having weakened portions, shown as grooves 3Gl (FIGURE so that the washer is automatically destroyed under the impact of the head of the anchoring stud at the end of the driving operation. The ribs 31 opposite grooves Si) on contact of the washer with the work surface cause a localized pressure on those portions of the washer which have been weakened by the grooves, and simplify its de- In FIGURE 6 is shown, in cross-section, a further embodiment of an easily destructible washer 53 such as of plastic. This washer has an inner flange 55 which labuts stud 23, and an outer ange 54 of greater width.

The splinter shield 3 is, together with its tubularly formed shaft 32, axially movable in a correspondingly dimensioned annular space between the outer wall of guide tube 2 and the inner wall of gripping shell 10. This splinter shield 3 is held in position by friction between the part 32r and the immediately adjacent elements. The splinter shield is provided with a member 33 made of an elastic material such as rubber. The rubber ring, which is fastened by means of sunken screws 34, has a Z- shaped proiile and surrounds, but is spaced from, the forward end of .the guide tube and the cylindrical casing 25.

Pivotally mounted in a chamber at the rearward end of guide tube 2 is a lever 3S. One end of this lever has a hook-shaped portion 39 which normally projects through the inner wall of the `guide tube (see FIGURE l) because of the action of a spring 40' pressing against the other end of the lever. During assembly of the apparatus, hookshaped portion 39 abuts the forward end of the cartridge carrier 5 to prevent it from moving towards piston 4, so that as knob 9 is moved towards tiring position (FIG- URE 3), spring 7 is compressed to develop the energy required for firing the shot.

Triggering occurs when the apparatus is in the position shown in FIGURE 3, by pressing a key 41 projecting through an opening in a casing 45 on one side of shell 10. In this manner, key end 43 passes through a corresponding opening 44 in housing 1, with compression of spring 42;, and presses on the forward end of the lever 38 so that hook-shaped portion 39 is withdrawn and the base of cartridge 13 isV driven, under the influence of springs, against the tiring pin 12 in the piston `4. As soon as this pin strikes the base of the cartridge, piston 4 is driven forward with the anchoring stud 23 under the influence of the combustion gases and the cartridge holder 6 with the cartridge carrier 5 is driven rearwards. When in this action, the cartridge holder 6 separates from rearward end 11 of the piston, the combustion gases expand through the axial grooves 14 and stream out under the splinter shield 3.

Key 41 is so located axially on the 'gripping shield 11i that it `can activate hook portion 39' of the lever 38 through opening 44 only lwhen the forward end of the guide tube 2 (with its cylindrical casing 2S) has been moved into the forward plane of the splinter shield 3 by pressure of the tool `against the work surface. Normally the rguide tube is maintained in its extended (safe) position as shown in FIGURE 2, preferably through spring action.

In order to exclude the possibility of a iiring without the splinter protective cap, a further locking key 46 is pivotally mounted under the pressure of a spring 47 in the sideward projecting casing 45 of gripping shell 1h', which locking key is not accessible from the exterior. Locking key 46, by gripping a stepped-in portion of guide tube 2 (i.e. when splinter shield 3 is absent) prevents the rearward shifting of yguide tube 2 in gripping shell 1b and thereby prevents free action of key 41 and lever `3 which comprise the trigger mechanism. if, however, as is shown in FIGURES l-3, the splinter shield 3 is present, the tubular shaft 32 of shield 3 holds the locking key 46 in a position where it will not interfere. Finally, the apparatus is provided with a safety mechanism that prevents the tiring of a shot so long as the bayonet closure 19, 2t? between the head piece and the housing 1 is not completely fastened. For this purpose, the tubularly formed head piece S has a recessed extension 51 having at one portion of its perimeter an axial slit 59. This slit is positioned opposite a nose-like projection 49 of retractable lever 39, when the parts are properly aligned, and allows the lever to retract for tiring.

The embodiment shown in FIGURES 7-15 comprises a cylindrical housing 161 surrounded by a gripping shell 102 having at its forward end a splinter shield 167, the tubular portion 103 of which is telescoped within the shell and held in place by locking key 109 (FIGURE lll). A guide tube .1@3 is movable in cylindrical housing 1111, and is normally held in the extended position shown in FIGURE 9V by means of a coil spring 11G located in the tube. The inner wall of the guide tube is provided with longitudinal grooves 111 through which the combustion gases may escape around the upper end V106 of a piston 1(15 and thence out through openings 103:1 into the interior of the splinter shield 1117.

A cartridge carrier 1114 and the piston 1115 are mounted for axial movement in the yguide tube 1%, the upper end of which is tapered outwardly to accommodate insertion of the cartridge carrier 104. These members are held in any desired position by means of friction elements 135 and 136. The rearward end 113 of the cartridge carrier is provided with an impact head 114 which also acts as a recoil damping mass. A pin 115 extends into a longitudinal groove 116 of the cartridge carrier to prevent rotation of the latter with respect to housing 1111. The cartridge 118 is held in such a position that its base faces the piston 165.

Piston 105 has at its forward end a cavity 119 to receive head 120 of anchoring stud 121, and has at its other end 10d a recess at the bottom of which is positioned a tiring pin 122. Axial piston ribs 137 (FGURE l2) engage the grooves 111 to prevent rotation .thereof with respect to guide tube 103. The point of the anchoring stud 121 is centered in a cavity of guide tube extension member 132, at the forward end of the vguide tube 163, by means of a washer held in place by permanent magnets 134. The guide tube extension member 132l provides a reduced-diameter bore which is axially aligned with the guide tube, and presents a shoulder around said bore to abut the corresponding shoulder formed by the upper end 105 of the piston member 165.

The cartridge carrier 104 has a band portion 112 formed with a circle of teeth 123 adapted to mesh with corresponding teeth 124 on the rim of the piston end 105, but this meshing can take place only when the piston andthe cartridge carrier are in a certain relative rotary position. Only in this position can the cartridge carrier extend so far into the cavity of the piston that firing pin 122 can contact the base of the cartridge 11% and bring about firing.

When the tool is in its normal position with the guide tube 163 extended out beyond splinter shield 107 (FIF- URE 9), the teeth 123 and 124 are misaligned, so that no firing can take place. However, when the tool is pressed against a work surface, the resultant inward movement of the guide tube produces a rotation of the guide tube, and thereby aligns the teeth 123 and 124 to permit ring after the front end of the tube has reached the forward plane of the splinter shield. This rotation of the guide tube is caused by the action of a cam pin 125, located on the outer side of the guide tube 193, which cooperates with guide slots 127 provi ed in housing 10'1.

The construction of the guide slots and the movements and positions possible therein for cam pin 126 are shown, diagrammatically, in FIGURES 13 and 14. The openings which comprise the `guide slots include an axial longitudinal .groove 12S which starts at the forward end of the housing 1M to accommodate the introduction of pin 126 into the guide slots on assembly of the apparatus. The rearward end of this groove 12S turns slightly to one side and forms a stop 129 for the pin. Two dead end branches communicate sidewards with the groove, of which the shorter branch 1331` extends toward the forward end of the tool at an angle of about 45 to the longitudinal axis, while the longer branch l131 extends off at an mgle toward the impact end of the tool. During assembly of the tool, guide tube 103 is inserted into the lower end of the housing 111 in such a way that cam pin 126 enters the groove 12%. As the guide tube is pressed upwardly into the housing, the pin 126 is cammed a small distance circumferentially and into the stop 129; thereafter, the guide tube is rotated manually a further distance circumferentially while being moved downwardly, this .combination of motions being such as to shift the cam pin l125 into the shor er branch 13d. Thus, after assembly of the apparatus (FIGURE 9), pin 125 will be in branch 13? (see FIGURE 13) and will be held there due to the pressure of spring 119 on guide tube 1413. By pressing the tool against the work surface, pin 126 engages the cam surfaces formed by the upper edges of branches 13d and 131 and thereby is made to follow the path shown by the arrow to the end of branch 131 (see FIGURE 14), whereby guide tube 163 is forced to rotate relative to housing 1111, and teeth 123 and 12d take a position such that meshing of the teeth, and tiring, is made possible.

ln using the tool, the first step is to take out the parts shown in FGURE 8, and then place cartridge 113 in the cartridge holder 117 with the cartridge carrier y"NT4-l moved forward as far as possible. The guide tube 133 with piston 105 then is inserted. In the above-described manner, cam pin 126 is guided through groove 12S and into branch 130, in which it is held by the pressure of spring 115i exerted against the guide tube (see FIG- URE 9). After the insertion of anchoring stud 121 in the cavity of the piston, the tool is positioned with the splinter shield 1617 against the work surface 12e. Thus, the piston and the cartridge carrier, by relative rotation, assume a position ready for firing with a small axial space between the teeth 123 and 124, so that a blow on impact head 114iwill cause ring by driving the cartridge down against the firing pin 122, whereby the combustion gases drive piston 1Go' forward so that the anchoring stud 121 is driven in.

I claim:

1. ln an explosively-operated stud-driving :tool of the type including a guide tube having rst and second plunger members slidably mounted therein, said first plunger member being positioned in the lower portion of said guide tube and arranged to apply a driving force to the stud, said second plunger member being positioned above said first plunger member, one of said members having a recess 4to receive a cartridge adapted to be red upon impact with the other of said members; apparatus comprising, in combination, an Iouter gripping shell within which said guide tube is movably mounted, said guide tube having means extendable beyond the lower end of said gripping shell to Contact the work surface of the material into which the stud is to be driven, means responsive to the relative rotational positioning of said plunger members for preventing cartridge tiring impact therebetween except when said two members are disposed with respect to each other in accordance with a predetermined rotational relationship, and rotating means responsive to the movement of said guide tube within said gripping shell, said rotating means being operable to rotate said two members into said predetermined rotational relationship when said guide tube is pressed against the work surface and thereby shifted interiorly with respect -to said gripping shell.

2. Apparatus as claimed in claim l, wherein said gripping shell is provided at its lower end with a splinter shield extending out laterally beyond Isaid guide tube.

3. Apparatus as claimed in claim 2, wherein said guide tube is provided adjacent its lower end with means having at least one opening to permit the escape of combustion gases into the interior of said splinter shield.

4. Apparatus as claimed in claim 1, wherein said cartridge recess is in the lower end of said second plunger member, said lsecond plunger member further being provided with a dead-end cavity communicating with the cartridge recess, the closed end `of the cavity being pointed.

5. Apparatus as claimed in claim 1, wherein the upper end of the guide tube is slightly tapered outwardly to facilitate insertion of said second plunger member.

6. Apparatus as claimed in claim 1, wherein said guide tube is provided at its lower end with means defining a reduced-diameter bore axially aligned with said guide tube, said first plunger member being provided with a shoulder to abut against a corresponding shoulder of said defining means around said bore, the part fof said first plunger member below the plunger shoulder being dimensioned to extend through said bore and project beyond the lower end.

7. Apparatus as claimed in claim 1, wherein said means responsive to the rotational positioning of said plunger members comprises interengageable means adjacent the ends of said plunger members.

8. Apparatus as claimed in claim 7, wherein said interengageable means comprises respective rings of teeth on said plunger members.

9. Explosively-actuated stud-driving apparatus of the type including a guide tube within which is slidably mounted first and second plunger members adapted to be stuck together, said first plunger member being positioned within the lower portion of said guide tube and adapted to apply driving force to the stud, one of said members having a recess to receive a cartridge adapted to be fired upon sharp impact with the other of said members; said apparatus comprising, in combination, an outer gripping shell within which said guide tube is slidably mounted, said guide tube being provided with contact means extendable beyond the lower end of said gripping shell to engage the work surface of the material into which the stud is to be driven, projections adjacent to the ends :of said plunger members for preventing cartridge firing impact except when said two members are in a predetermined relative rotational position, said other member being formed with an axial recess to receive the part of said one member carrying the cartridge so that the cartridge can be fired by impact thereof against `the bottom of said axial recess, and rotating means responsive to the movement of said guide tube within said gripping shell, said rotating means being operable to produce relative rotation between said two arcanes `impact with the other of said members, said `other member being formed with an arial recess arranged to receive the part of said one plunger member carrying said cartridge, whereby the cartridge can be tired by impact thereof against the bottom of said axial recess formed in said other plunger member,

11. Apparatus as claimed in claim 10, wherein said cartridge is carried by said second plunger member, the part of said second plunger member carrying said cartridge being cylindrical in shape, Isaid axial recess being formed in said first plunger member and dimensioned to tit closely with said cylindrical part of said second plunger member.

.12. Apparatus as claimed in claim 1l, wherein said second plunger member is provided on its side with means slidably received in said guide tube, the portion of said second plunger member below said last named means being spaced inwardly from said guide tube.

13. Apparatus as claimed in claim 10, wherein said axial recess is provided in its bottom with firing pin means to tire the cartridge upon impact therewith.

14. In an eXplosively-operated stud-driving tool lot the type including a guide tube carrying rst and second plunger members slidably mounted therein, said rst plunger member being positioned in the lower portion of said guide tube and adapted to apply a driving force to the stud, one of said plunger members having a recess to receive a cartridge adapted to be tired upon sharp impact with the other of said plunger members; apparatus comprising, in combination, an outer gripping shell within which said guide tube is mounted for axial movement, means for preventing cartridge tiring impact between )said two plunger members except when said guide tube and said outer gripping shell are disposed rotationally relative to one another in accordance with a predetermined relationship, and rotating means responsive to the movement of said guide tube within saidV gripping shell, said rotating means being operable to rotate said guide tube with respect to said gripping shell nd into said predete ned relationship when sai guide tube is pressed against the Work surface and thereby shifted interiorly with respect to said gripping shell.

15. Apparatus as claimed in claim 14, wherein said rotating means comprises a cam pin carried by said guide tube, said gripping shell including .an element having a slot therein in which said cam pin lits, said slot being disposed in a direction having a component which extends circumferentially around said gripping shell, whereby axial movement of said guide tube within said gripping shell produces relative rotational movement of said guide tube.

16. Apparatus as claimed in claim 15, wherein said rst plunger member is non-rotatably mounted with respect to said guide tube, said second plunger member being non-rotatabiy mounted with respect to said gripping shell, said means for preventing firing impact comprising interengageable means adjacent the ends of said irst and second plunger members.

17. Apparatus as claimed in claim 16, wherein said guide tube is formed on its interior surface with at least one longitudinal groove, said rst plunger member having means engaged with said groove to prevent relative rotation therebetween.

18. Apparatus `as claimedin claim 15, wherein said slot includes .a longitudinal groove beginning at the lower end of said shell element, the upper end of this groove being turned slightly in a circumferential direction, and two dead end branches communicating with said groove, one of said branches extending at an angle of about 45 with respect to the longitudinal aXis of the tool and toward the lower end thereof, the other branch extending towards the upper end of the tool at a s'nnilar angle and being slightly longer than the iirst branch, said rst branch providing a safe position for the cam pin wherein cartridge tiring impact is prevented, spring means urging said cam pin into said safe position, the second `of said branches providing a ready-to-ire position into which the cam pin is moved by pushing the guide tube back against the compression of sai-d spring means.

References Cited in the tile of this patent UNTTED STATES PATENTS UNITED STATES PATENT OFFICE CERTIFICATE 0F CORRECTION Patent No. 3l05238 October' l, 1963 Martin Hilti It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below Column 6, line 55, for "stuck" read struck -n Signed and sealed this 7th day of April l94 (SEAL) Attest:

EDWARD Ja BRENNER ERNEST W., SWIDER Attesting Officer Commissioner of Patents 

1. IN AN EXPLOSIVELY-OPERATED STUD-DRIVING TOOL OF THE TYPE INCLUDING A GUIDE TUBE HAVING FIRST AND SECOND PLUNGER MEMBERS SLIDABLY MOUNTED THEREIN, SAID FIRST PLUNGER MEMBER BEING POSITIONED IN THE LOWER PORTION OF SAID GUIDE TUBE AND ARRANGED TO APPLY A DRIVING FORCE TO THE STUD, SAID SECOND PLUNGER MEMBER BEING POSITIONED ABOVE SAID FIRST PLUNGER MEMBER, ONE OF SAID MEMBERS HAVING A RECESS TO RECEIVE A CARTRIDGE ADAPTED TO BE FIRED UPON IMPACT WITH THE OTHER OF SAID MEMBERS; APPARATUS COMPRISING, IN COMBINATION, AN OUTER GRIPPING SHELL WITHIN WHICH SAID GUIDE TUBE IS MOVABLY MOUNTED, SAID GUIDE TUBE HAVING MEANS EXTENDABLE BEYOND THE LOWER END OF SAID GRIPPING SHELL TO CONTACT THE WORK SURFACE OF THE MATERIAL INTO WHICH THE STUD IS TO BE DRIVEN, MEANS RESPONSIVE TO THE RELATIVE ROTATIONAL POSITIONING OF SAID PLUNGER MEMBERS FOR PREVENTING CARTRIDGE FIRING IMPACT THEREBETWEEN EXCEPT WHEN SAID TWO MEMBERS ARE DISPOSED WITH RESPECT TO EACH OTHER OTHER IN ACCORDANCE WITH A PREDETERMINED ROTATIONAL RELATIONSHIP, AND ROTATING MEANS RESPONSIVE TO THE MOVEMENT OF SAID GUIDE TUBE WITHIN SAID GRIPPING SHELL, SAID ROTATING MEANS BEING OPERABLE TO ROTATE SAID TWO MEMBERS INTO SAID PREDETERMINED ROTATIONAL RELATIONSHIP WHEN SAID GUIDE TUBE IS PRESSED AGAINST THE WORK SURFACE AND 